Sequential or Waste spark?

[Garth AE86]

Wow, you really do like throwing money about!! Holden charge a mint for any of thier newish gear... even the VN/VP stuff is rediculous. The VP rear tail lights that go on the bootlid(the mini ones) are $240 new trade from holden... imagine what the coil packs are worth??

Cheers, Owen

Really? Kinda strage the coils are so cheap then...

a set of 4 trade was $70 if i recall?

[roadsailing]

i'll have a look at the gen 3/4 coils, from hazy memory they are denso.

[Bored?]

So the bottom line for all of this is that the maximum RPM supported by a "sequential" setup is double that which can be supported for a wasted spark setup, for any given ignition technology.

One reason to use CDI is if the engine revs are high enough that peak inductor current cannot be reached between successive ignition events[1][2]. This is likely to happen:

1. using a single coil + distributor setup[3]
2. if you have a true high-rpm engine[4]

The other reason to use CDI would be for when even a fully charged inductor doesn't store enough energy for each spark. In This case a CDI system, which just uses the coil as a step-up transformer rather than an energy storage device, could help. This is sometimes the case for turbo cars running high boost.

Anyway, for your a low rpm road car engine, regardless of whether you have CDI or not, it probably doesn't matter whether you choose wasted spark or not.

1. "Dwell time" is just the time required to charge the inductor. It is not a function of RPM.
2. Google for "inductor transient response" if you want to understand what is going on.
3. The problem gets worse for engines with more cylinders.
4. Not likely in a road car, but maybe in a race car or motorcycle.